The present invention relates to transparent flame retardant injection moldable blends of aromatic polycarbonate copolymer having up to 5 mole percent of chemically combined silylarylsiloxy units, such as silylarylimide units or silylarylester units, based on the total moles of condensed silylarylsiloxy units and aromatic dihydric phenol carbonate units. More particularly, the present invention relates to the employment of a triarylsilicon material, such as a hexaaryldisiloxane, in combination with the aromatic polycarbonate copolymer to produce flame retardant blends capable of being injection molded to specific shapes having thicknesses of less than 1/8", while exhibiting V-O UL-94 test values.
Prior to the present invention, as shown by copending application by Policastro et al., Ser. No. 7/319,026, filed Mar. 6, 1989, certain poly(arylenesilicon) materials, such as the silicon-polycarbonate block copolymers of J. Rich et al., Ser. No. 07/319,025, filed Mar. 6, 1989, now U.S. Pat. No. 4,945,148 or the polyestersiloxane block copolymers of Policastro et al., Ser. No. 07/319,027, filed Mar. 6, 1989 now U.S. Pat. No. 4,945,147 were blended with aromatic polycarbonates resins to produce flame retardant aromatic polycarbonate blends. It was found, however, that although the resulting blends of aromatic polycarbonate resin and poly(arylenesilicon) material resulted in the production of flame retardant injection moldable materials, a thickness of 1/8" or greater of the aromatic polycarbonate blend was required to achieve a V-O UL-94 test value.
In copending application Ser. No. 07/399,094, filed 8/28/89, Lewis et al., and Ser. No. 07/399,095, filed Aug. 28, 1989, Lewis, filed concurrently herewith, it was found that if an effective amount of a triarylsilicon material, such as triphenylvinylsilane, or a silicate resin, were incorporated into a finely divided aromatic polycarbonate, such as Lexan polycarbonate, a 1/16" compression molded polycarbonate test slab could be made exhibiting UL-94 V-O properties.
It would be desirable therefore to provide flame retardant, aromatic polycarbonates which could be injection molded for certain applications at 1/16" and be capable of satisfying the V-O UL-94 test requirements. These requirements are shown by the Flammability of Plastic Materials Bulletin, Jan. 24, 1980. More particularly, a 5".times.1/2".times.1/16" polycarbonate test bar containing an effective amount, as defined hereinafter, of arylene silicon material of the present invention, is suspended vertically over a 3/4" Bunsen Burner flame as provided in the aforementioned UL-94 test. The test sample preferably exhibits a UL-94 V-O rating which includes the following criteria:
A. Not have any specimen which burn with flaming combustion for more than 10 seconds after application of the test flame.
B. Not have a total flaming combustion time exceeding 50 seconds for 10 flame applications for each set of five specimens.
C. Not have any specimens which burn with flaming or glowing combustion up to the holding clamp.
D. Not have any specimens which drip flaming particles that ignite dry absorbent surgical cotton located 12 inches (305 mm) below the test specimen.
E. Not have any specimens with glowing combustion which persists for more than 30 seconds after the second removal of the test flame.